"I don't think (the talks) are going to fail, and that is because neither side has a better means of achieving its fundamental objectives," Sir Richard John Dalton, British Ambassador to Iran from 2002 to 2006, told the BBC in an interview on Wednesday.
"For the international community and the United States, that's a high level of assurance that Iran will stick to its commitments and never militarize its nuclear program, and for Iran that it gets some of its internationally linked economy back."
"Another reason for optimism is that President Trump's language has been consistent despite the threats which he should dial down," Dalton continued. "It's been consistent in expressing preference for sorting matters out through dialogue."
Dalton added that a statement by the foreign ministry of Oman, the country mediating the talks, following the latest US-Iran meeting on Saturday pointed to a framework for a successful deal.
"It included 'fair'. That means win-win, something for both sides. 'Enduring': this is vitally important because of the absence of any trust in Tehran that the United States is capable of sticking to agreements that it signs."
"'Binding': again endorsed by the international community, may be something which puts constraints on both sides that go beyond the actual words of the agreement. Then, 'Iran free of nuclear weapons' ... but Iran having its right to 'peaceful nuclear energy' that was in the Omani statement too, together with Iran being free of sanctions."
"Now this is the big win potentially for Iran, because its economy has been in tatters for many years, and the most significant threat to the survival of the regime is instability caused by potential breakdown of the economy," he said.